There are several techniques available for contacting syngas with Fischer-Tropsch catalysts. For example, the catalyst can be contained in a fixed bed or it may be contained in a fluidized bed. Alternatively, the catalyst may be slurried in an inert solvent and the syngas can be bubbled up there through. The use of a slurry phase provides for the possibility for making additions to the slurry phase which will modify the catalytic reactivity of the catalyst without having to directly incorporate these additives in the catalyst per se. For example, these additives may not be easily incorporated into the catalyst or they might be readily leached out of the catalyst by the reaction products, in which case the use of a slurry phase incorporating an inert solvent provides a means for maintaining these additives in the reacting system.